JP4659605B2 - Image forming apparatus and image forming method - Google Patents

Description

  The present invention relates to an electrophotographic or electrostatic recording image forming apparatus such as a copying machine or a printer, and an image forming method used in the image forming apparatus.

  Various types of image forming apparatuses for forming a color image on a transfer material using an electrophotographic recording method have been proposed, and some of them have been put into practical use (for example, see Patent Document 1).

  FIG. 7 is a side view schematically showing the main internal structure of a color image forming apparatus employing the inline method. This image forming apparatus is configured as an inline type color printer of a quadruple photosensitive drum-intermediate transfer type.

  This in-line type color printer includes an intermediate transfer belt 106, which is suspended from a driving roller 107, a driven roller 109, and a tension roller 108, and is rotationally driven in the direction of arrow A in the figure. Along the intermediate transfer belt 106, four photosensitive drums 101a to 101d as image carriers are arranged in series. The photosensitive drum 101 and other image forming means constitute arrangement stations PY, PM, PC, and PK in which image forming means for forming yellow, magenta, cyan, and black toner images are arranged.

  The image forming units of the arrangement stations PY, PM, PC, and PK are each configured as follows. That is, it is composed of photosensitive drums 101a to 101d, chargers 102a to 102d, exposure units 103a to 103d, developing units 104a to 104d, and photosensitive drum cleaners 105a to 105d arranged around the photosensitive drums 101a to 101d. The image forming units for the respective colors have substantially the same configuration except that yellow, magenta, cyan, and black toners are accommodated in the developing units 104a to 104d, respectively.

  A four-color full-color image forming operation will be described. First, each photosensitive drum 101 rotates, and the surface thereof is uniformly charged by the charger 102. Next, a laser beam modulated in accordance with image data is irradiated from the exposure device 103, and a desired electrostatic latent image corresponding to each color is formed on the surface of each photosensitive drum 101. The electrostatic latent images on the respective photosensitive drums 101 are developed at developing positions using toner by the respective developing units 104 and visualized as yellow, magenta, cyan, and black toner images, respectively.

  The toner images of the respective colors formed on the photosensitive drum 101 are electrostatically transferred onto the intermediate transfer belt 106 while being sequentially superposed by the transfer roller 110 of the transfer unit at each transfer nip portion facing the photosensitive drum 101. The transfer material P is supplied from the paper feeding unit to the secondary transfer nip portion of the intermediate transfer belt 106 and the secondary transfer roller 112 via the conveying unit, and the toner images on the intermediate transfer belt 106 are electrostatically collectively transferred. .

  The toner remaining on the photosensitive drum 101 by the transfer is removed by the photosensitive drum cleaner 105 having a cleaning blade or the like, and is prepared for the next image forming process.

  The toner remaining on the intermediate transfer belt 6 by the secondary transfer is removed by the intermediate transfer belt cleaner 111 to prepare for the next image forming process.

The four color toner images transferred onto the transfer material P in this way are formed on the transfer material P as shown in FIG. In FIG. 8, M represents magenta toner, C represents cyan toner, Y represents yellow toner, and K represents black toner.
JP 2001-183885 A (page 13, FIG. 10)

  Here, the toner layer is fixed to the transfer material P by applying pressure and heat in the fixing nip by the fixing roller 126 and the pressure roller 127 in the fixing unit 125 shown in FIG.

At this time, if the storage elastic modulus G ′ _{(T) at the} temperature (T) reached in the fixing nip of each toner during the fixing process is low, when pressure and heat are applied to the toner layer, FIG. As a result, excessive penetration of the toner layer into the transfer material may occur. As a result, paper fibers appear on the image surface as shown in FIG. 10, the uniformity of the glossiness on the image surface is lost, the image density is lowered, and a desired image cannot be obtained. there were.

Therefore, the storage elastic modulus G ′ _(T) reaching the fixing nip of each toner during the fixing process can be increased by lowering the temperature reached in the fixing nip during the fixing process or changing the type of the toner itself. It was thought. However, with this method, the toner is not sufficiently melted, and the glossiness of the image surface is lowered, or the fixability of the toner image to the transfer material is deteriorated. As a result, a desired image can be obtained. There was a problem that disappeared.

  The present invention has been made in view of the above problems, and its objects are as follows. That is, the present invention provides an image forming apparatus and an image forming apparatus that can sufficiently melt a toner image in a fixing step to obtain a desired glossiness, and that can prevent excessive penetration of the toner image into a transfer material. It aims to provide a method. As a result, it is possible to stably obtain a high-quality image having a uniform glossiness on the image surface, no image density reduction, and good fixability.

  The above problems can be solved by the image forming apparatus and the image forming method according to the present invention.

(1) In the image forming apparatus for forming a multicolor toner image by superimposing a plurality of colored toners, the present invention develops white toner according to the multicolor toner image and performs transfer, thereby transferring the transfer material. and an image forming apparatus for performing an image forming step of forming a white toner image, a fixing step of fixing the multi-color toner image and the white toner image on the transfer material between the multicolor toner image, the type K50μm thermoelectric When the maximum temperature in the temperature rise curve in the fixing nip measured by pasting the pair on the recording paper and passing through the fixing paper together with the recording paper is the ultimate temperature (T) in the fixing nip, storage elastic modulus at ultimate temperature (T) in the fixing nip of the white toner during fixing step G _{'(T) (W)} is, fixing process when the individual reaches the temperature in the fixing nip of the organic color toner (T storage elastic in) Higher than, and, said storage modulus G _{'(T) (W),} characterized in that it is 1.0 × ¹⁰ 4 dyn / cm ² or more 1.0 × ¹⁰ 6 dyn / cm ² or less An image forming apparatus.

The image forming apparatus of the present invention forms a white toner image between the transfer material and the multicolor toner image. Then, as shown in FIG. 6, the storage elastic modulus G ′ _(T) (W) at the temperature reached in the fixing nip of the white toner during the fixing process is expressed as the temperature reached in the fixing nip of the colored toner during the fixing process. Set higher than the storage elastic modulus at. In this way, it is possible to make a difference in the viscosity at the time of melting of the toner layer, the toner closer to the transfer material is less likely to be melted, and the toner on the image surface side is easily melted. Thereby, excessive penetration into the transfer material can be suppressed, and desired glossiness can be obtained on the image surface.

Further, the storage elastic modulus G ′ _(T) (W) at the temperature reached in the fixing nip of the white toner during the fixing step is 1.0 × 10 ⁴ dyn / cm ² or more and 1.0 × 10 ⁶ dyn / cm. Set to ² or less. As a result, the white toner in contact with the transfer material can be melted to such an extent that it does not soak into the transfer material excessively and does not impair the fixability.

(2) In the image forming apparatus for forming a multicolor toner image by superimposing a plurality of color toners, the present invention develops the transparent toner according to the multicolor toner image, and performs transfer, thereby transferring the transfer material. Forming apparatus that performs an image forming process for forming a transparent toner image between the toner and the multicolor toner image, and a fixing process for fixing the multicolor toner image and the transparent toner image on the transfer material, type K50 μm When the maximum temperature in the temperature rise curve in the fixing nip measured by attaching a thermocouple to the recording paper and passing through the fixing paper together with the recording paper is the ultimate temperature (T) in the fixing nip, fixing process at the arrival temperature in the fixing nip of the transparent toner (T) storage modulus G _{'(T) (the} to) is, fixing process when the individual reaches the temperature in the fixing nip of the organic color toner (T storage bullets in) Rate G 'higher than _(T), and said storage modulus G' _{(T) (To)} is located at 1.0 × ¹⁰ 4 dyn / cm ² or more 1.0 × ¹⁰ 6 dyn / cm ² or less An image forming apparatus characterized by the above.

The image forming apparatus of the present invention forms a transparent toner image between a transfer material and a multicolor toner image. Then, as shown in FIG. 6, the storage elastic modulus G ′ _(T) (To) at the temperature reached in the fixing nip of the transparent toner during the fixing step is expressed as the temperature reached in the fixing nip of the colored toner during the fixing step. Set higher than the storage elastic modulus at. In this way, it is possible to make a difference in the viscosity at the time of melting of the toner layer, the toner closer to the transfer material is less likely to be melted, and the toner on the image surface side is easily melted. Thereby, excessive penetration into the transfer material can be suppressed, and desired glossiness can be obtained on the image surface.

Further, the storage elastic modulus G ′ _(T) (To) at the temperature reached in the fixing nip of the transparent toner during the fixing step is 1.0 × 10 ⁴ dyn / cm ² or more and 1.0 × 10 ⁶ dyn / cm. Set to ² or less. As a result, the transparent toner in contact with the transfer material can be melted to such an extent that it does not soak into the transfer material excessively and does not impair the fixability.

(3) Further, according to the present invention, in the image forming method for forming a multicolor toner image by superimposing a plurality of colored toners, a white toner is developed according to the multicolor toner image, and transfer is performed. Forming method for forming a white toner image between the toner and the multicolor toner image, and a fixing step for fixing the multicolor toner image and the white toner image on the transfer material, type K50 μm When the maximum temperature in the temperature rise curve in the fixing nip measured by attaching a thermocouple to the recording paper and passing through the fixing paper together with the recording paper is the ultimate temperature (T) in the fixing nip, fixing process when the white toner reaches the temperature of the fixing nip (T) storage modulus G _{'(T) (W)} is, fixing process when the individual reaches the temperature in the fixing nip of the organic color toner ( storage bullets in T) Higher than the rate, and the reservoir modulus G _{'(T) (W),} characterized in that it is 1.0 × ¹⁰ 4 dyn / cm ² or more 1.0 × ¹⁰ 6 dyn / cm ² or less An image forming method.

The image forming method of the present invention forms a white toner image between a transfer material and a multicolor toner image. Then, as shown in FIG. 6, the storage elastic modulus G ′ _(T) (W) at the temperature reached in the fixing nip of the white toner at the fixing step is expressed as the inside of the fixing nip of the colored toner at the fixing step. Is set higher than the storage elastic modulus at the ultimate temperature. In this way, it is possible to make a difference in the viscosity at the time of melting of the toner layer, the toner closer to the transfer material is less likely to be melted, and the toner on the image surface side is easily melted. Thereby, excessive penetration into the transfer material can be suppressed, and a desired glossiness can be obtained on the image surface.

Further, the storage elastic modulus G ′ _(T) (W) at the temperature reached in the fixing nip of the white toner during the fixing step is 1.0 × 10 ⁴ dyn / cm ² or more and 1.0 × 10 ⁶ dyn /. Set to cm ² or less. As a result, the white toner in contact with the transfer material can be melted to such an extent that it does not soak into the transfer material excessively and does not impair the fixability.

(4) Further, according to the present invention, in an image forming method in which a plurality of colored toners are superimposed to form a multicolor toner image, the transparent toner is developed in accordance with the multicolor toner image and transferred to perform transfer. an image forming step of forming a transparent toner image between the wood and the multi-color toner image, an image forming method for performing a fixing step of fixing the multi-color toner image and the white toner image on the transfer material, type When the maximum temperature in the temperature rise curve in the fixing nip measured by pasting a K50 μm thermocouple on the recording paper and passing it through the fixing device together with the recording paper is the ultimate temperature (T) in the fixing nip storage modulus G reaches a temperature (T) in the fixing nip of the transparent toner at the fixing step _{'(T) (the} to) is reached the temperature of the fixing nip of each of the organic color toner during fixing step savings in (T) Higher than the elastic and reservoir modulus G _{'(T) (To),} characterized in that it is 1.0 × ¹⁰ 4 dyn / cm ² or more 1.0 × ¹⁰ 6 dyn / cm ² or less An image forming method.

The image forming method of the present invention forms a transparent toner image between a transfer material and a multicolor toner image. Then, as shown in FIG. 6, the storage elastic modulus G ′ _(T) (To) at the temperature reached in the fixing nip of the transparent toner during the fixing step is expressed as the temperature reached in the fixing nip of the colored toner during the fixing step. Set higher than the storage elastic modulus at. In this way, it is possible to make a difference in the viscosity at the time of melting of the toner layer, the toner closer to the transfer material is less likely to be melted, and the toner on the image surface side is easily melted. Thereby, excessive penetration into the transfer material can be suppressed, and desired glossiness can be obtained on the image surface.

Furthermore, the storage elastic modulus G ′ _(T) (To) at the temperature reached in the fixing nip of the transparent toner during the fixing step is 1.0 × 10 ⁴ dyn / cm ² or more and 1.0 × 10 ⁶ dyn / Set to cm ² or less. As a result, the white toner in contact with the transfer material can be melted to such an extent that it does not soak into the transfer material excessively and does not impair the fixability.

  As described above, according to the present invention, the toner image can be sufficiently melted in the fixing step to obtain a desired gloss level, and the toner image can be prevented from excessively penetrating into the transfer material. A forming apparatus and an image forming method can be provided. As a result, it is possible to stably obtain a high-quality image having a uniform glossiness on the image surface, no image density reduction, and good fixability.

  Hereinafter, embodiments according to the present invention will be described in more detail with reference to the drawings.

  The ultimate temperature (T) in the fixing nip during the fixing process in this example was determined as follows. First, a type K 50 μm thermocouple is attached to a transfer material such as recording paper, and the recording paper is passed through the fixing device together with the recording paper to obtain a temperature rise curve in the fixing nip. The maximum temperature in the obtained temperature rise curve was defined as the ultimate temperature (T) in the fixing nip.

  Further, the storage elastic modulus G 'of the toner in this example was measured using a dynamic viscoelasticity measuring apparatus such as Rheometric RMS-800.

The specific measurement method is as follows. First, about 1 gram of sample was fixed between the plates on the parallel plate test fixture (heated at about 110 ° C. for several minutes), and one side gave a strain of 62.8 rad / sec of torsional reciprocating motion. Is detected. At this time, the distortion rate was automatic (maximum 20%). In this state, the temperature was raised and the temperature dependence of viscoelasticity was measured. From this result, the storage elastic modulus G ′ _(T) of the toner at the temperature reached in the fixing nip (T [° C.]) during the fixing process was obtained.

  Further, in the fixability test of the fixed image in this example, the obtained image was rubbed 10 times back and forth with a load of about 100 g, and the peeling of the image was evaluated by the reduction rate (%) of the reflection density.

  In the fixability test, if the reduction rate of the reflection density of the image is 10% or less, the fixability is good. In addition, if the reduction rate exceeds 20%, when the user is using the image, not only characters will be peeled off and the halftone image will be blurred, but also the hand, clothes and other paper will be stained. Is not preferable.

  Further, for evaluation of glossiness and gloss uniformity of a fixed image in this example, a gloss meter VG2000 (trade name) manufactured by Nippon Denshoku Industries Co., Ltd. was used, and a 60-degree specular gloss according to JIS Z 8741. It was measured by the degree measurement method and evaluated.

  In addition, the density evaluation of the fixed image in this example was performed by measuring the reflection density of the fixed image using Gretag Macbeth RD918 (trade name) as a reflection density measuring device. Further, Gretag Macbeth TD904 (trade name) was used as a transmission density measuring device, and evaluation was performed by measuring the transmission density of a fixed image.

Further, as a method for changing the value of the storage elastic modulus G ′ _{(T) at} the temperature reached in the fixing nip of the toner described in the present embodiment, the following can be mentioned. For example, there is a method of changing the ultimate temperature (T) in the fixing nip by changing the temperature setting of the fixing roller, and consequently changing the ultimate temperature storage elastic modulus G ′ _(T) in the fixing nip. Further, the viscoelasticity of the toner is changed by changing the molecular weight and molecular weight distribution of the binder resin of the toner, the cross-linking rate of the polymer chain, and the like. As a result, the storage elastic modulus G ′ at the temperature reached in the fixing nip is changed. _A method of changing _(T) is also possible.

  Examples of the binder resin for toner include the following. Polyesters, polystyrenes; polymer compounds obtained from styrene derivatives such as poly-p-chlorostyrene and polyvinyltoluene; styrene-p-chlorostyrene copolymers, styrene-vinyltoluene copolymers, styrene-vinylnaphthalene copolymers, Styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer Styrene copolymer such as polymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer; polyvinyl chloride, phenol resin, modified phenol resin, male resin, acrylic resin, methacrylic resin, polyvinyl acetate, Ricone resin; polyester resin having a monomer selected from aliphatic polyhydric alcohol, aliphatic dicarboxylic acid, aromatic dicarboxylic acid, aromatic dialcohol and diphenol as a structural unit; polyurethane resin, polyamide resin, polyvinyl Butyral, terpene resin, coumarone indene resin, petroleum resin.

  In the method of directly obtaining toner particles by the polymerization method, the following monomers are preferably used. Styrene; o (m-, p-)-methylstyrene, styrene monomer such as m (p-)-ethylstyrene; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, (Meth) butyl acrylate, octyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, behenyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dimethyl (meth) acrylate (Meth) acrylic acid ester monomers such as aminoethyl and diethylaminoethyl (meth) acrylate; ene monomers such as butadiene, isoprene, cyclohexene, (meth) acrylonitrile and acrylic acid amide.

  In the toner, it is preferable to use at least silica fine particles and / or titanium oxide fine particles as an external additive because fluidity can be favorably imparted to the developer and the life of the developer is improved. Further, by using these fine powders, a developer with less environmental fluctuation is obtained.

  Examples of other external additives include the following. Metal oxide fine powder (aluminum oxide, strontium titanate, cerium oxide, magnesium oxide, chromium oxide, tin oxide, zinc oxide, etc.), nitride fine powder (silicon nitride, etc.), carbide fine powder (silicon carbide, etc.), metal Salt fine powder (calcium sulfate, barium sulfate, calcium carbonate, etc.), fatty acid metal salt fine powder (zinc stearate, calcium stearate, etc.), carbon black, resin fine powder (polytetrafluoroethylene, polyvinylidene fluoride, polymethyl methacrylate) , Polystyrene, silicone resin, etc.). These external additives may be used alone or in combination. It is more preferable that the external additives including the silica fine powder have been subjected to a hydrophobic treatment.

  The mixing treatment of the toner particles and the external additive can be performed using a mixer such as a Henschel mixer.

  Examples of the colorant used in the toner include the following.

  As the yellow colorant, compounds typified by condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and allylamide compounds are used. Specifically, C.I. I. Pigment Yellow 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 109, 110, 111, 128, 129, 147, 168 can be suitably used.

  As the magenta colorant, condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinones, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds are used. Specifically, C.I. I. Pigment Red 2, 3, 5, 6, 7, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 144, 146, 166, 169, 177, 184, 185, 202, 206, 220, 221, and 254 can be suitably used.

  Examples of cyan colorants include copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds, and basic dye lake compounds. Specifically, C.I. I. Pigment Blue 1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62, 66 can be preferably used.

  These colorants can be used alone or in combination and further in the form of a solid solution.

  Examples of the black colorant include carbon black, a magnetic material, and a color toned to black using the yellow / magenta / cyan colorant described above.

  Examples of white colorants include zinc white, titanium oxide, antimony white, and zinc sulfide.

  In the case of a color toner, the colorant is selected in consideration of hue angle, chroma, lightness, weather resistance, OHP transparency, and dispersibility in the toner. The content of the colorant is preferably 1 to 20 parts by mass with respect to 100 parts by mass of the binder resin for toner.

  Known charge control agents can be used for the toner. In the case of a color toner, in particular, a charge control agent that is colorless or light in color, has a high toner charging speed, and can stably maintain a constant charge amount is preferable. Furthermore, in the present invention, when a toner is produced using a polymerization method, a charge control agent free from a solubilized product in an aqueous medium having a polymerization inhibition property is particularly preferable.

  The following are used as negative charge control agents. Metallic compounds of salicylic acid, dialkylsalicylic acid, naphthoic acid, dicarboxylic acid or derivatives thereof; polymeric compounds having sulfonic acid or carboxylic acid in the side chain; boron compounds; urea compounds; silicon compounds; As the positive charge control agent, the following are used. A quaternary ammonium salt; a polymer compound having the quaternary ammonium salt in the side chain; a guanidine compound; and an imidazole compound. The content of the charge control agent is preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the binder resin. However, the addition of a charge control agent to the toner particles is not essential.

  Examples of the method for producing toner particles include the following. For example, there is a method in which a binder resin, a colorant, and other internal additives are melt-kneaded, and the kneaded product is cooled and then pulverized and classified. Further, the toner particles are directly generated using a suspension polymerization method. Further, it is a dispersion polymerization method in which toner particles are directly produced using an aqueous organic solvent which is soluble in the monomer and insoluble in the polymer obtained. Further, the toner particles are produced by using an emulsion polymerization method represented by a soap-free polymerization method in which toner particles are directly polymerized in the presence of a water-soluble polar polymerization initiator.

  When toner particles are produced by a polymerization method, for example, the following are used as polymerization initiators. 2,2′azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carbonitrile, 2,2′-azobis-4 -Azo polymerization initiators such as methoxy-2,4-dimethylvaleronitrile and azobisisobutyronitrile; benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide Such peroxide polymerization initiators.

  Although the addition amount of a polymerization initiator changes with the target degree of polymerization, generally 0.5 to 20 mass% is added and used with respect to a monomer. The kind of the polymerization initiator varies slightly depending on the polymerization method, but can be used alone or in combination with reference to the 10-hour half-life temperature. A known crosslinking agent, chain transfer agent, polymerization inhibitor, etc. for controlling the degree of polymerization can be further added and used.

  When suspension polymerization is used as a toner production method, the following can be used as long as the dispersant is an inorganic oxide. Tricalcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate, bentonite, silica, alumina . Examples of organic compounds include the following. Polyvinyl alcohol, gelatin, methyl cellulose, methyl hydroxypropyl cellulose, ethyl cellulose, carboxymethyl cellulose sodium salt, starch. These are used by being dispersed in an aqueous phase. These dispersants are preferably used in an amount of 0.2 to 10.0 parts by mass with respect to 100 parts by mass of the polymerizable monomer.

  As these dispersants, commercially available ones may be used as they are, but in order to obtain dispersed particles having a fine uniform particle size, the inorganic compound can be produced in a dispersion medium under high-speed stirring. For example, in the case of tricalcium phosphate, a preferred dispersant for the suspension polymerization method can be obtained by mixing an aqueous sodium phosphate solution and an aqueous calcium chloride solution under high-speed stirring. Moreover, you may use together 0.001 to 0.1 mass part surfactant for refinement | miniaturization of these dispersing agents. Specifically, commercially available nonionic, anionic or cationic surfactants as described below can be used. Sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pendadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium laurate, potassium stearate, calcium oleate.

  When a direct polymerization method is used as a toner production method, the toner can be produced specifically by the following production method. Dispersing and stabilizing a monomer composition that has been uniformly dissolved or dispersed by means of a homogenizer, ultrasonic disperser, etc. by adding a release agent, a colorant, a charge control agent, a polymerization initiator or other additives to the monomer The mixture is dispersed in the aqueous phase containing the agent by a stirrer, a homomixer, a homogenizer or the like. Preferably, the droplets made of the monomer composition are granulated by adjusting the stirring speed and time so as to have a desired toner particle size. Thereafter, stirring may be performed to such an extent that the particle state is maintained and the sedimentation of the particles is prevented by the action of the dispersion stabilizer. Polymerization is carried out at a polymerization temperature of 40 ° C. or higher, generally 50 to 90 ° C. The temperature may be raised in the latter half of the polymerization reaction, and for the purpose of improving the durability, a part of the aqueous medium is retained after the latter half of the reaction or after the completion of the reaction in order to remove unreacted polymerizable monomers and byproducts. You may leave. After completion of the reaction, the produced toner particles are recovered by washing and filtration and dried. In the suspension polymerization method, it is usually preferable to use 300 to 3000 parts by weight of water as a dispersion medium with respect to 100 parts by weight of the monomer system.

  In the present invention, the color toner means toner excluding transparent toner and white toner. Specifically, the color toner is preferably at least one toner selected from the group consisting of yellow toner, magenta toner, cyan toner and black toner. Further, a color toner with an increased amount of colorant and a color toner with a reduced amount of colorant may be used in combination.

In the present invention, the storage elastic modulus at the ultimate temperature (T) of the white toner in the fixing nip is G ′ _(T) (W), and the storage elastic modulus of the transparent toner at the ultimate temperature (T) in the fixing nip is G ′ _{( T)} Shown as (To). Further, the storage elastic modulus at the arrival temperature (T) in the fixing nip of yellow toner is G ′ _(T) (Y), and the storage elastic modulus at the arrival temperature (T) in the fixing nip of magenta toner is G ′ _(T). (M). Further, the storage elastic modulus at the arrival temperature (T) in the fixing nip of the cyan toner is G ′ _(T) (C), and the storage elastic modulus at the arrival temperature (T) in the fixing nip of the black toner is G ′ _(T). Shown as (K).

Here, when white toner, yellow toner, magenta toner, cyan toner and black toner are used, the relationship of the storage elastic modulus at the temperature (T) reached in the fixing nip of each toner is as follows. preferable.
G ′ _(T) (W)> G ′ _(T) (Y)
G ′ _(T) (W)> G ′ _(T) (M)
G ′ _(T) (W)> G ′ _(T) (C)
G ′ _(T) (W)> G ′ _(T) (K)
Further, when transparent toner, yellow toner, magenta toner, cyan toner and black toner are used, the relationship of the storage elastic modulus at the temperature (T) reached in the fixing nip of each toner is preferably as follows. .
G ′ _(T) (To)> G ′ _(T) (Y)
G ′ _(T) (To)> G ′ _(T) (M)
G ′ _(T) (To)> G ′ _(T) (C)
G ′ _(T) (To)> G ′ _(T) (K)

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  The toners in the examples and comparative examples were produced using the following method.

[Method for producing white toner 1]
3 parts by mass of tricalcium phosphate is added to 900 parts by mass of ion-exchanged water heated to 70 ° C., and stirred at 10,000 rpm using a TK homomixer (made by Tokushu Kika Kogyo Co., Ltd.) to obtain an aqueous medium. It was.
Styrene 80.0 parts by mass n-butyl acrylate 20.0 parts by mass divinylbenzene 1.0 part by mass Saturated polyester resin 4.5 parts by mass (polycondensate of propylene oxide-modified bisphenol A and isophthalic acid,
Glass transition temperature (Tg) = 65 ° C., number average molecular weight (Mn) = 17000, weight average molecular weight (Mw) / number average molecular weight (Mn) = 2.4)
Aluminum salicylate compound (Bontron E-88, manufactured by Orient Chemical Co., Ltd.) 1.0 part by mass Antimony white 6.0 parts by mass The above materials are uniformly dispersed and mixed using an attritor (Mitsui Miike Chemical Co., Ltd.). A functional monomer composition was prepared. The polymerizable monomer composition was heated to 63 ° C., and 9 parts by mass of an ester wax mainly composed of stearyl stearate was added, mixed and dissolved therein, and a polymerization initiator 2,2′-azobis-2-methyl was added thereto. A polymerizable monomer mixture was prepared by dissolving 3 parts by mass of butyronitrile.

The polymerizable monomer mixture was put into an aqueous medium, and the mixture was granulated by stirring at 10,000 rpm for 7 minutes with a TK homomixer at 63 ° C. in an N ₂ atmosphere. Thereafter, the mixture was reacted at 63 ° C. for 6 hours while stirring with a paddle stirring blade. Thereafter, the liquid temperature was raised to 80 ° C., and stirring was further continued for 4 hours. After completion of the reaction, the mixture was cooled, hydrochloric acid was added to the suspension cooled to room temperature (25 ° C.) to dissolve the calcium phosphate salt, filtered and washed with water to obtain wet toner particles.

  Next, the toner particles were dried at 40 ° C. for 12 hours to obtain toner particles having a weight average particle diameter of 7.6 μm.

100 parts by weight of the toner particles and 0.7 parts by weight of a hydrophobic silica fine powder having a BET value of 200 m ² / g and a primary particle size of 12 nm treated with silicone oil were mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd. )) To obtain white toner 1.

[Method for producing white toner 2]
As shown in Table 1, white toner 2 was obtained using the same production method as white toner 1 except that 0.8 parts by mass of divinylbenzene was used.

[Method for Producing White Toner 3]
As shown in Table 1, white toner 3 was obtained using the same production method as white toner 1 except that 2.0 parts by mass of divinylbenzene was used.

[Method for Producing White Toner 4]
As shown in Table 1, white toner 4 was obtained using the same production method as white toner 1 except that 0.6 parts by mass of divinylbenzene was used.

[Method for producing transparent toner 1]
A transparent toner 1 was obtained using the same production method as the white toner 1 except that no white pigment was used.

[Method for producing yellow toner 1, magenta toner 1, cyan toner 1 and black toner 1]
White toner except that 0.5 parts by weight of divinylbenzene was used and 6.0 parts by weight of yellow colorant (CI Pigment Yellow 74) was used instead of white colorant (antimony white) Yellow toner 1 was obtained using the same production method as in No. 1.
A magenta toner 1 was obtained using the same production method as the yellow toner 1 except that 6.0 parts by mass of a magenta colorant (CI Pigment Red 122) was used instead of the yellow colorant.
Further, cyan toner 1 was obtained using the same production method as yellow toner 1 except that 6.0 parts by mass of cyan colorant (CI Pigment Blue 15: 3) was used instead of yellow colorant. It was.
A black toner 1 was obtained using the same production method as that of the yellow toner 1 except that 6.0 parts by mass of carbon black was used instead of the yellow colorant.

[Production Method of Yellow Toner 2, Magenta Toner 2, Cyan Toner 2 and Black Toner 2]
Yellow toner 2 was obtained using the same production method as yellow toner 1 except that 1.5 parts by mass of divinylbenzene was used.
Magenta toner 2 was obtained using the same production method as magenta toner 1 except that 1.5 parts by mass of divinylbenzene was used.
Cyan toner 2 was obtained using the same production method as cyan toner 1 except that 1.5 parts by mass of divinylbenzene was used.
A black toner 2 was obtained using the same production method as that of the black toner 1 except that 1.5 parts by mass of divinylbenzene was used.

Example 1
FIG. 1 is a block diagram showing an embodiment of an image forming apparatus of the present invention. This image forming apparatus is an inline intermediate transfer type color printer in which four arrangement stations PY to PK and an arrangement station PW for arranging a cartridge filled with white toner 1 are arranged in parallel along the intermediate transfer belt 6. .

The feature of this embodiment is that a developing device for storing white toner 1 is provided in addition to four developing devices for storing colored toners such as yellow toner 1, magenta toner 1, cyan toner 1 and black toner 1, respectively. The storage elastic modulus G ′ _(T) (W) at the temperature reached in the fixing nip of the white toner during the fixing step is greater than the storage elastic modulus at the temperature reached in the fixing nip of the colored toner during the fixing step. Is also expensive. Further, the storage elastic modulus G ′ _(T) (W) at the temperature reached in the fixing nip of the white toner during the fixing step is 1.0 × 10 ⁴ dyn / cm ² or more and 1.0 × 10 ⁶ dyn / cm. It is within the range of ² or less.

As a result of measuring the ultimate temperature (T) in the fixing nip and the storage elastic modulus of each color toner in this embodiment, G ′ _(T) (W) is 2.0 × 10 ⁵ , G ′ _(T) (Y ), G ′ _(T) (M), G ′ _(T) (C) and G ′ _(T) (K) were all 1.5 × 10 ⁴ . The results are shown in Table 2.

  The image forming operation in this image forming apparatus will be described below with reference to FIG.

  The photosensitive drums 1a to 1e rotate, the surfaces thereof are uniformly charged by the chargers 2a to 2e, and then the laser beams modulated according to the image data are irradiated from the exposure units 3a to 3e. A desired electrostatic latent image corresponding to each color is formed on the surface of 1e.

  Here, a laser beam modulated according to all colored image data is irradiated from the exposure device 3e onto the photosensitive drum 1e in the arrangement station PW, and a desired electrostatic latent image is formed on the surface of the photosensitive drum 1e. The

  The electrostatic latent images on the photosensitive drums 1a to 1e are developed at the development positions using toner by the developing units 4a to 4e, and visualized as yellow, magenta, cyan, black, and white toner images, respectively.

  By the above image forming operation, first, a yellow toner image is formed on the photosensitive drum 1a at the first color arrangement station PY. During this time, a transfer material P such as recording paper is supplied from a recording material storage unit 22 such as a cassette by a paper feed roller 23 and conveyed to a pair of registration rollers 24. The transfer material P is temporarily stopped by the registration roller pair 24. As the transfer belt 6 rotates, the yellow toner image on the photosensitive drum 1a is transferred onto the intermediate transfer belt 6 by a voltage opposite to the toner applied to the transfer roller 10a disposed inside the transfer belt 6 at the transfer portion. Is electrostatically transferred to.

  Next, in the arrangement stations PM, PC, PK, and PW for the second, third, fourth, and fifth colors, magenta, cyan, black, and white are formed on the photosensitive drums 1b, 1c, 1d, and 1e through the same process. A toner image is formed. Next, the images are sequentially transferred onto the intermediate transfer belt 6 to obtain a color image obtained by multiple transfer of a four-color toner image and a white toner image on the intermediate transfer belt 6.

  The toner remaining on the photosensitive drum 1 by the transfer is removed by a drum cleaner 5 equipped with a cleaning blade or the like, and is prepared for the next image forming process.

  Thus, the transfer material P once stopped by the registration roller pair 24 is supplied to the secondary transfer nip portion between the intermediate transfer belt 6 and the secondary transfer roller 12 at a predetermined timing, and the toner on the intermediate transfer belt 6 is transferred. The image is electrostatically transferred collectively.

  The toner remaining on the intermediate transfer belt 6 by the secondary transfer is removed by an intermediate transfer belt cleaner (not shown) to prepare for the next image forming process.

  As shown in FIG. 3, the four-color and white toner images collectively transferred onto the transfer material P in this way form a white toner image at a position in contact with the transfer material P, as shown in FIG. Colored toner is formed on the surface. In FIG. 3, M represents magenta toner, C represents cyan toner, Y represents yellow toner, K represents black toner, and W represents white toner.

  Thereafter, the toner layer is fixed to the transfer material P by applying pressure and heat in the fixing nip by the fixing roller 26 and the heating roller 27 in the fixing unit 25.

  Here, the fixing unit 25 in this embodiment will be described in detail.

  The fixing roller 26 has a concentric three-layer structure, and has a core portion, an elastic layer, and a release layer. This core portion is constituted by an aluminum hollow pipe having a diameter of 44 mm and a thickness of 5 mm. The elastic layer is made of silicon rubber having a JIS-A hardness of 50 degrees and a thickness of 3 mm. The release layer is composed of PFA (copolymer of tetrafluoroethylene and perfluoroalkoxyethylene) having a thickness of 50 μm. Note that a halogen lamp as a heat source is disposed inside the hollow pipe of the core portion. The heating roller 27 has the same configuration.

  In addition, power is supplied to a halogen lamp (not shown) disposed inside the fixing roller 26 and the heating roller 27, and the surface temperatures of the fixing roller 26 and the heating roller 27 rise.

  The fixing roller 26 is pressed at both ends by a pressure spring (not shown), and a fixing nip is formed by the pressure contact between the fixing roller 26 and the heating roller 27. The applied pressure at this time is about 80 kgf.

  Further, the fixing nip width in this embodiment is about 10 mm.

  Hereinafter, the behavior of the toner image in the fixing nip in this embodiment will be described in detail.

As shown in FIG. 4, the toner layer is fixed to the transfer material P by applying pressure and heat in the fixing nip by the fixing roller 26 and the heating roller 27 in the fixing unit 25. At this time, as shown in Table 2, the storage elastic modulus G ′ _(T) (W) at the temperature (T) reached in the fixing nip of the white toner in contact with the transfer material is expressed in the fixing nip of each color toner. The value is higher than the storage elastic modulus at the ultimate temperature (T). For this reason, the white toner transferred in the vicinity of the transfer material P is less soluble than the colored toner on the image surface side, and the toner image is prevented from excessively penetrating into the transfer material. Further, since the toner on the image surface side is easily melted, the toner image surface is sufficiently melted. Further, the storage elastic modulus G ′ _(T) (W) at the temperature (T) reached in the fixing nip during the fixing process of the white toner is 1.0 × 10 ⁴ dyn / cm ² or more and 1.0 × 10 ^6. It is set within a range of dyn / cm ² or less. For this reason, the white toner transferred in the vicinity of the transfer material P melts to such an extent that it does not soak into the paper fibers of the transfer material P and does not impair the fixing property.

  That is, the white toner transferred in the vicinity of the transfer material P prevents excessive penetration of the multicolor toner image into the transfer material, and the colored toner on the image surface is sufficiently melted. Then, as shown in FIG. 5, a high-quality image having a uniform glossiness on the surface of the image and having a good fixability without a decrease in image density is discharged by the discharge roller pair 28.

As described above, in this embodiment, an image forming apparatus including a developing unit that stores white toner in addition to four developing units that store colored toners such as yellow toner, magenta toner, cyan toner, and black toner is used. Then, the white toner is developed in accordance with a multicolor toner image and transferred to form an image forming step for forming a white toner image between the transfer material and the multicolor toner image, and A fixing process for fixing the color toner image and the white toner image, and the storage elastic modulus G ′ _(T) (W) at the temperature (T) at which the white toner reaches the fixing nip during the fixing process is determined as the fixing process. The storage elastic modulus G ′ _{(T) at a} temperature reached in the fixing nip of the white toner during the fixing step is higher than the storage elasticity at the temperature reached in the fixing nip of the colored toner during the fixing step _(T). When (W) is in the range of 1.0 × 10 ⁴ dyn / cm ^{2 to} 1.0 × 10 ⁶ dyn / cm ² , the white toner in contact with the transfer material is Prevents excessive penetration into the transfer material and is colored The toner can be sufficiently melted during the fixing step, and a high-quality image having a uniform glossiness on the surface of the image and good fixability without a decrease in image density can be stably obtained.

(Example 2)
This embodiment is different from the first embodiment in that an in-line direct transfer type image forming apparatus is used and a white toner 2 is used instead of the white toner 1.

  About the other structure, the thing similar to Example 1 was used.

  FIG. 2 is a block diagram showing an embodiment of the image forming apparatus of the present invention. The image forming apparatus is an in-line direct transfer type color printer in which four arrangement stations PY to PK and an arrangement station PW for arranging a cartridge filled with white toner are arranged along the paper transport belt 16.

The feature of this embodiment is that it includes a developing unit for storing white toner in addition to four developing units for storing colored toners such as yellow toner, magenta toner, cyan toner and black toner. The storage elastic modulus G ′ _(T) (W) at the temperature (T) reached in the fixing nip of the white toner during the fixing step is the temperature reached (T) of the colored toner in the fixing nip during the fixing step. Higher than the storage modulus in Further, the storage elastic modulus G ′ _(T) (W) at the temperature (T) reached in the fixing nip of the white toner during the fixing step is 1.0 × 10 ⁴ dyn / cm ² or more and 1.0 × 10 ^6. It is in the range of dyn / cm ² or less.

  Table 2 shows the results of measuring the ultimate temperature (T) in the fixing nip and the storage elastic modulus of each color toner in this example.

  The image forming operation in this image forming apparatus will be described below.

  The photosensitive drums 1a to 1e rotate, the surfaces thereof are uniformly charged by the chargers 2a to 2e, and then the laser beams modulated according to the image data are irradiated from the exposure units 3a to 3e. A desired electrostatic latent image corresponding to each color is formed on the surface of 1e.

  Here, a laser beam modulated according to all colored image data is irradiated from the exposure device 3e onto the photosensitive drum 1e in the arrangement station PW, and a desired electrostatic latent image is formed on the surface of the photosensitive drum 1e. The

  The electrostatic latent images on the photosensitive drums 1a to 1e are developed at developing positions using toner by the developing units 4a to 4e, respectively, and are toner images of yellow toner, magenta toner, cyan toner, black toner, and white toner, respectively. Is visualized as

  By the above image forming operation, first, a white toner image is formed on the photosensitive drum 1e at the first color arrangement station PW. During this time, the transfer material P is supplied from the recording material storage unit 22 such as a cassette by the paper feed roller 23 and conveyed to the registration roller pair 24. The transfer material P is temporarily stopped by the registration roller pair 24. Thereafter, the transfer material P is transported onto the paper transport belt 16 by the rotation of the registration roller pair 24 at a predetermined timing, and transported to the transfer section by the paper transport belt 16. In the transfer unit, the white toner image on the photosensitive drum 1e is electrostatically transferred onto the transfer material P by a voltage opposite in polarity to the toner applied to the transfer roller 10e disposed inside the paper transport belt 16. .

  Next, in the second color, third color, fourth color, and fifth color arrangement stations PK, PC, PM, and PY, black, cyan, magenta, and yellow are formed on the photosensitive drums 1b, 1c, 1d, and 1e through the same process. A toner image is formed. Subsequently, the image is sequentially transferred onto the transfer material P, and a color image is obtained in which the four-color toner image and the white toner image are transferred onto the transfer material P on the paper transport belt 16 in a multiple transfer manner.

  The toner remaining on the photosensitive drum 1 by the transfer is removed by a drum cleaner 5 equipped with a cleaning blade or the like, and is prepared for the next image forming process.

  The four-color and white toner images collectively transferred onto the transfer material P in this way are white toner at a position in contact with the transfer material P on the transfer material P as shown in FIG. An image is formed and colored toner is formed thereon. In FIG. 3, M represents magenta toner, C represents cyan toner, Y represents yellow toner, K represents black toner, and W represents white toner.

  Thereafter, the toner layer is fixed to the transfer material P by applying pressure and heat in the fixing nip by the fixing roller 26 and the heating roller 27 in the fixing unit 25.

  The behavior of the toner image in the fixing nip in this embodiment will be described in detail.

As shown in FIG. 4, the toner layer is fixed to the transfer material P by applying pressure and heat in the fixing nip by the fixing roller 26 and the heating roller 27 in the fixing unit 25. At this time, as shown in Table 2, the storage elastic modulus G ′ _(T) (W) at the temperature reached in the fixing nip of the white toner in contact with the transfer material is the temperature at the temperature reached in the fixing nip of each color toner. The value is higher than the storage elastic modulus. For this reason, the white toner transferred in the vicinity of the transfer material P is less soluble than the colored toner on the image surface side, and the toner image is prevented from excessively penetrating into the transfer material. Further, since the toner on the image surface side is easily melted, the toner image surface is sufficiently melted. Further, the storage elastic modulus G ′ _(T) (W) reached in the fixing nip during the fixing step of the white toner is 1.0 × 10 ⁴ dyn / cm ² or more and 1.0 × 10 ⁶ dyn / cm ² or less. It is set within the range. For this reason, the white toner transferred in the vicinity of the transfer material P melts to such an extent that it does not soak into the paper fibers of the transfer material P and does not impair the fixing property.

  That is, excessive penetration of the toner image into the transfer material is prevented by the white toner transferred in the vicinity of the transfer material P, and the colored toner on the image surface is sufficiently melted. Then, as shown in FIG. 5, a high-quality image having a uniform glossiness on the surface of the image and having a good fixability without a decrease in image density is discharged by the discharge roller pair 28.

As described above, even if a direct transfer type image forming apparatus is used as described in the present embodiment, a step of forming a white toner image between the transfer material and the multicolor toner image is performed, and The storage elastic modulus G ′ _(T) (W) at the temperature reached in the fixing nip of the white toner is higher than the storage elastic modulus at the temperature reached in the fixing nip of each colored toner, and at the time of the fixing step The storage elastic modulus G ′ _(T) (W) at the temperature reached in the fixing nip of the white toner is in the range of 1.0 × 10 ⁴ dyn / cm ^{2 to} 1.0 × 10 ⁶ dyn / cm ^2. As a result, similarly to the first embodiment, a high-quality image having a uniform glossiness on the image surface and good fixability without a decrease in image density can be stably obtained.

Further, as described in this embodiment, even when a white toner having a different resin characteristic is used, the storage elastic modulus G ′ _(T) (W _{) at the} temperature reached in the fixing nip of the white toner in the fixing step. ) Is higher than the storage elastic modulus at the temperature reached in the fixing nip of each color toner, and the storage elastic modulus G ′ _(T) (W) of the white toner in the fixing nip during the fixing process is If it is set in the range of 1.0 × 10 ⁴ dyn / cm ² or more and 1.0 × 10 ⁶ dyn / cm ² or less, the effect of the present invention can be obtained similarly.

(Example 3)
In this embodiment, an image forming apparatus in which a cartridge filled with a transparent toner 1 is arranged instead of a cartridge filled with a white toner 1 in the arrangement station PW of FIG. Using.

In addition, the feature of this embodiment is that a developing device for storing transparent toner is provided in addition to four developing devices for storing colored toners such as yellow toner, magenta toner, cyan toner and black toner. The storage elastic modulus G ′ _(T) (To) at the temperature reached in the fixing nip of the transparent toner at the fixing step is larger than the storage elastic modulus at the temperature reached in the fixing nip of the colored toner at the fixing step. high. Further, the storage elastic modulus G ′ _(T) (To) at the temperature reached in the fixing nip of the transparent toner during the fixing step is 1.0 × 10 ⁴ dyn / cm ² or more and 1.0 × 10 ⁶ dyn / cm. It is within the range of ² or less.

  Table 2 shows the results of measuring the ultimate temperature (T) in the fixing nip and the storage elastic modulus of each color toner in this example.

  The image forming operation in this image forming apparatus is the same as that in Example 1. As a result of performing the image forming operation in this example, the following effects were obtained. That is, the transparent toner in contact with the transfer material prevented excessive penetration of the toner image into the transfer material, and the colored toner was sufficiently melted during the fixing step. As a result, it is possible to stably obtain a high-quality image having a uniform glossiness on the image surface and good fixability without a decrease in image density.

  In addition, the shape of the member shown by the present Example is not restricted to this.

(Comparative Example 1)
In this comparative example, the same image forming apparatus and toner as in Example 1 were used except that the white toner 3 was used instead of the white toner 1. At this time, storage elastic moduli G ′ _(T) (Y), G ′ _(T) (M), G ′ _(T) (C), G ′ _{( T)} (K) and G ′ _(T) (W) are shown in Table 2, respectively.

As a result of performing the same image forming operation as in Example 1, the storage elastic modulus G ′ _(T) (W) at the temperature reached in the fixing nip of the white toner at the fixing step is determined as the fixing nip of the colored toner at the fixing step. The storage elastic modulus higher than the storage elastic modulus at the ultimate temperature was used, but the storage elastic modulus G ′ _(T) (W) of the white toner in the fixing nip during the fixing process was 1.0 × 10 ⁶ dyn / cm. ^{When the} value is larger than ^2, the melting of the white toner in contact with the transfer material becomes insufficient, and an image with insufficient fixability of the toner image to the transfer material such as recording paper is discharged.

(Comparative Example 2)
In this comparative example, white toner 4, yellow toner 2, magenta toner 2, cyan toner 2 and black toner 2 were used instead of white toner 1, yellow toner 1, magenta toner 1, cyan toner 1 and black toner 1. Except for this, the same image forming apparatus as in Example 1 was used. At this time, storage elastic moduli G ′ _(T) (Y), G ′ _(T) (M), G ′ _(T) (C), G ′ _{( T)} (K) and G ′ _(T) (W) are shown in Table 2, respectively.

As a result of performing the same image forming operation as in Example 1, the storage elastic modulus G ′ _(T) (W) at the temperature reached in the fixing nip of the white toner during the fixing process is 1.0 × 10 ⁴ dyn / cm. ^When it was less than ² , excessive penetration into the transfer material occurred when the white toner in contact with the transfer material was melted, and paper fibers appeared on the image surface. As a result, the uniformity of the glossiness of the image surface was lost, and an image in which a desired image density could not be obtained was discharged.

(Comparative Example 3)
In this comparative example, the same procedure as in Example 1 was performed except that yellow toner 2, magenta toner 2, cyan toner 2 and black toner 2 were used instead of yellow toner 1, magenta toner 1, cyan toner 1 and black toner 1. Image forming apparatus and toner were used. At this time, storage elastic moduli G ′ _(T) (Y), G ′ _(T) (M), G ′ _(T) (C), G ′ _{( T)} (K) and G ′ _(T) (W) are shown in Table 2, respectively.

As a result of performing the same image forming operation as in Example 1, the storage elastic modulus G ′ _(T) (W) at the temperature reached in the fixing nip of the white toner at the fixing step is determined as the fixing nip of the colored toner at the fixing step. Since the toner having a lower storage elastic modulus at the ultimate temperature was used, the color toner on the image surface was not sufficiently melted, the glossiness of the image surface was lowered, and a desired image could not be obtained.

Fixability evaluation A: Good fixability was obtained.
B: Slightly difficult to fix.
C: The image sometimes peeled off.
Glossiness evaluation A: A desired glossiness was obtained.
B: A slight decrease in glossiness was observed.
C: A desired glossiness could not be obtained.
Evaluation of density and gloss uniformity A: A uniform gloss was obtained, and no decrease in density occurred.
B: A slightly non-uniform gloss was observed, but no decrease in density occurred.
C: Unevenness was observed in the gloss, and the density decreased.

1 is a configuration diagram showing an embodiment of an image forming apparatus of the present invention. It is a block diagram which shows the 2nd Example of the image forming apparatus of this invention. FIG. 6 is an explanatory diagram illustrating an overlapping state of toner layers after transfer in an example of the present invention. FIG. 6 is an explanatory diagram illustrating a state where toner layers overlap during fixing in an exemplary embodiment of the present invention. FIG. 6 is an explanatory diagram illustrating an overlapping state of toner layers after fixing according to an exemplary embodiment of the present invention. It is explanatory drawing which shows the temperature dependence of the storage elastic modulus of the toner in this invention. It is a block diagram which shows an example of the conventional image forming apparatus. It is explanatory drawing which shows the overlapping state of the toner layer after the transfer in a prior art example. FIG. 10 is an explanatory diagram showing a toner layer overlapping state at the time of fixing in a conventional example. FIG. 10 is an explanatory diagram illustrating a state of overlapping toner layers after fixing in a conventional example.

Explanation of symbols

1a to 1e Photosensitive drum 4a to 4e Developer PY / PM / PC / PK Colored toner placement station PW White toner placement station PT Transparent toner placement station P Transfer material

Claims (8)

In an image forming apparatus for forming a multicolor toner image by superimposing a plurality of colored toners, a white toner is developed in accordance with the multicolor toner image, and transfer is performed so that the transfer material and the multicolor toner image are transferred. An image forming apparatus that performs an image forming process for forming a white toner image between the image forming apparatus and a fixing process for fixing the multicolor toner image and the white toner image to the transfer material;
The maximum temperature in the temperature rise curve in the fixing nip measured by pasting a type K 50 μm thermocouple on the recording paper and passing it through the fixing device together with the recording paper is defined as the ultimate temperature (T) in the fixing nip. when the storage modulus G reaches a temperature in the fixing nip of the white toner during fixing step _{(T) '(T) (} W) is reached in the fixing nip of each of the organic color toner during fixing step Higher than the storage modulus at temperature (T) , and
The image forming apparatus, wherein the storage elastic modulus G ′ _(T) (W) is 1.0 × 10 ⁴ dyn / cm ² or more and 1.0 × 10 ⁶ dyn / cm ² or less.   2. The image forming apparatus according to claim 1, wherein the colored toner is at least one toner selected from the group consisting of yellow toner, magenta toner, cyan toner and black toner. In an image forming apparatus for superimposing a plurality of colored toners to form a multicolor toner image, the transparent toner is developed in accordance with the multicolor toner image and transferred to thereby transfer the transfer material and the multicolor toner image. An image forming apparatus that performs an image forming process for forming a transparent toner image between the image forming apparatus and a fixing process for fixing the multicolor toner image and the transparent toner image on the transfer material,
The maximum temperature in the temperature rise curve in the fixing nip measured by pasting a type K 50 μm thermocouple on the recording paper and passing it through the fixing device together with the recording paper is defined as the ultimate temperature (T) in the fixing nip. when the storage modulus G reaches a temperature in the fixing nip of the transparent toner at the fixing step _{(T) '(T) (} to) is reached in the fixing nip of each of the organic color toner during fixing step Higher than the storage modulus at temperature (T) , and
The image forming apparatus, wherein the storage modulus G ′ _(T) (To) is 1.0 × 10 ⁴ dyn / cm ² or more and 1.0 × 10 ⁶ dyn / cm ² or less.   4. The image forming apparatus according to claim 3, wherein the colored toner is at least one toner selected from the group consisting of yellow toner, magenta toner, cyan toner, and black toner. In an image forming method in which a plurality of colored toners are overlapped to form a multicolor toner image, white toner is developed in accordance with the multicolor toner image and transferred to transfer the transfer material between the multicolor toner image. An image forming step of forming a white toner image on the transfer material, and a fixing step for fixing the multicolor toner image and the white toner image on the transfer material,
The maximum temperature in the temperature rise curve in the fixing nip measured by pasting a type K 50 μm thermocouple on the recording paper and passing it through the fixing device together with the recording paper is defined as the ultimate temperature (T) in the fixing nip. when the storage modulus G reaches a temperature in the fixing nip of the white toner during fixing step _{(T) '(T) (} W) is reached in the fixing nip of each of the organic color toner during fixing step Higher than the storage modulus at temperature (T) , and
The image forming method, wherein the storage elastic modulus G ′ _(T) (W) is 1.0 × 10 ⁴ dyn / cm ² or more and 1.0 × 10 ⁶ dyn / cm ² or less.   6. The image forming method according to claim 5, wherein the colored toner is at least one toner selected from the group consisting of yellow toner, magenta toner, cyan toner and black toner. In an image forming method in which a plurality of colored toners are superimposed to form a multicolor toner image, the transparent toner is developed in accordance with the multicolor toner image and transferred, so that the transfer material and the multicolor toner image are transferred. An image forming method comprising: an image forming step of forming a transparent toner image; and a fixing step of fixing the multicolor toner image and the transparent toner image to the transfer material;
The maximum temperature in the temperature rise curve in the fixing nip measured by pasting a type K 50 μm thermocouple on the recording paper and passing it through the fixing device together with the recording paper is defined as the ultimate temperature (T) in the fixing nip. when the storage modulus G reaches a temperature in the fixing nip of the transparent toner at the fixing step _{(T) '(T) (} to) is reached in the fixing nip of each of the organic color toner during fixing step Higher than the storage modulus at temperature (T) , and
The image forming method, wherein the storage elastic modulus G ′ _(T) (To) is 1.0 × 10 ⁴ dyn / cm ² or more and 1.0 × 10 ⁶ dyn / cm ² or less.   8. The image forming method according to claim 7, wherein the colored toner is at least one toner selected from the group consisting of yellow toner, magenta toner, cyan toner and black toner.

Images